Two recently reported, randomized, double blinded trials have demonstrated the efficacy of high titer hepatitis B immune globulin (HBIG) in affording temporary passive immunity to individuals accidentally exposed to low doses of HBsAg-positive material. In both studies, a 5 ml injection of HBIG was given within one week of exposure and a second injection one month later. This dosage schedule was chosen arbitrarily. A single dose schedule of HBIG has proven efficacious in prophylaxis of spouses exposed to hepatitis B. However, these two dosage schedules, single injection and divided injections, have never been compared in a controlled study. This study plans to enroll 300 individuals accidentally exposed to hepatitis B positive materials for development of hepatitis. Candidates were to be randomized in a double blinded fashion and treated with the same dose of HBIG in either a single or double injection. Two hundred and ninety-six individuals have been enrolled. Samples were collected at monthly intervals, following exposure, for six months and at 9 and 12 months.